One of the key goals of current research in data-driven computer animation is the synthesis of new motion sequences from existing motion data. This thesis presents three novel techniques for synthesising the motion of a virtual character from existing motion data and develops a framework of solutions to key character animation problems. The first motion synthesis technique presented is based on the character's locomotion composition process. This technique examines the ability of synthesising a variety of character's locomotion behaviours while easily specified constraints (footprints) are placed in the three-dimensional space. This is achieved by analysing existing motion data, and by assigning the locomotion behaviour transition process to transition graphs that are responsible for providing information about this process. However, virtual characters should also be able to animate according to different style variations. Therefore, a second technique to synthesise real-time style variations of character's motion. A novel technique is developed that uses correlation between two different motion styles, and by assigning the motion synthesis process to a parameterised maximum a posteriori (MAP) framework retrieves the desire style content of the input motion in real-time, enhancing the realism of the new synthesised motion sequence. The third technique presents the ability to synthesise the motion of the character's fingers either o↵-line or in real-time during the performance capture process. The advantage of both techniques is their ability to assign the motion searching process to motion features. The presented technique is able to estimate and synthesise a valid motion of the character's fingers, enhancing the realism of the input motion. To conclude, this thesis demonstrates that these three novel techniques combine in to a framework that enables the realistic synthesis of virtual character movements, eliminating the post processing, as well as enabling fast synthesis of the required motion.

There is a trend in the power industry for high temperature components (such as steam pipe work) to be operated in an increasingly arduous fashion. This would involve the use of elevated steam temperatures/pressures and a greater frequency of start up/shut down cycles. Such generation strategies are being adopted due to the need for thermally efficient power supply that can match fluctuating market demands. If these generation strategies are to be implemented safely it is critical that careful analysis of the system components is conducted in order to ensure that premature failure does not occur. The advanced material models and techniques that are used in academia to simulate these components are often out of reach of the engineers working in industry. The present work describes the development of an analysis “toolbox” that takes several advanced material models (which can accommodate complex loading conditions) and applies them in numerical (finite element analysis, FEA) and approximate life estimation methods. The toolbox comprises several modules, each of which relates to a specific aspect of component analysis. In this thesis, the fundamental procedures behind these modules are developed in novel ways in addition to the development of the toolbox as a whole. The toolbox modules may be roughly divided into the definition of a component’s material, geometry and loading condition, followed by some form of analysis procedure and a report of the key results. A material’s behaviour is commonly determined from mechanical tests. For in service components, scoop sampling is an exciting new method to extract small amounts of material which may then be tested using several novel small specimen techniques. An investigation has been conduced in the present work that verifies the safety of this method and allows the localised stress behaviour around an excavation to be estimated. Material constants in material behaviour models are usually determined by fitting the outputs of the model to experimental data in an optimisation procedure. A great deal of work has been completed on this topic using the complex Chaboche unified visco-plasticity model. This has led to the formation of the combined parallel optimisation strategy and the development of data cleaning for the determination of material constants in any model. Due to the high temperature conditions power plant components operate in, creep is a major concern. Several damage material models have been compared which can represent failure due to creep. Generally, these models can be divided into power law and hyperbolic sine functions. Through a comparative investigation using multiple component geometries, it has been found that the hyperbolic sine function creep law gives lower predictions of failure time than the power law models at realistic stress levels. Hyperbolic sine function failure lives were also more representative of reality. It is therefore critical when performing component analysis to consider the form of a material model as well as the loading range its material constants are applicable to. The Chaboche unified visco-plasticity model has also been discussed. Using this model, both hardening due to the accumulation of plastic strain and viscous effects (such as creep stress relaxation) may be described. Models like this will play an important role in the analysis of high temperature components as they experience fluctuations in both load and temperature. Although it appears simple, the geometry of a high temperature pipe bend in a power plant is actually complex due to the manufacturing process employed (a straight pipe section is heated through induction coils and bent using a fixed radius arm). The pipe’s wall thickness not only varies circumferentially around the pipe’s cross section but also around the bend itself. Through the analysis of industrial data (collected by ultrasonic measurement of components during outage inspections) several novel geometry factors have been developed that quantify this dimension variation. A new method to analyse such pipe bends has also been created that interpolates the stress states between two dimensional (2D) models that represent the cross section of a pipe bend at several key locations. Once a geometry, loading condition and material has been defined, an analysis procedure may be employed in order to assess the condition of the component. As creep is a key concern under high temperature conditions, most of the analysis procedures discussed in the present work are focused on the prediction of peak rupture stresses (δR) which may be used to estimate failure lives due to creep. Several approximate (errors are typically less than 5%) parametric relationships have been developed that allow peak rupture stresses to be determined based on, for example, pipe bend geometry factors. In addition, to aid in bespoke FEA analyses, a collection of routines with a graphical user interface (GUI) have been created that can write input files for a commercial FEA code (ABAQUS), run the job and post process the results. This can save a great amount of user effort when attempting to analyse components. Finally, an original neural network (that uses a partially connected, multiple input node architecture) has been proposed that predicts δR in pipe bends operating under steady-state creep conditions. Both internal pressure and system loads have been incorporated as inputs for this neural network. This has required the definition of several new load factors that describe the system loads acting on a component. Recommendations for future developments based on this research have also been given. Future developments may look to include fatigue effects in parametric equations, as well as considering the effect of varying loading conditions (possibly through a damage fraction approach). The Chaboche model (or similar unified model) may be modified to include temperature dependency and damage effects (allowing for a wider application to component analysis). The effect of geometry variation may be included in the neural network, again extending its applicability, and stresses due to temperature distributions in the piping components may be incorporated (at present, these have not been considered, however system loads may be thermally driven). The work presented in this thesis addresses a complete analysis procedure, from collecting material information from a component through scoop sampling, to determining material constants for this material by an optimisation procedure and analysing the component using either numerical or approximate methods. Although pipe bends have been considered for the significant part of this work due to the relatively small amount of research reported in literature, similar methodologies may be applied to other power plant components of interest, such as welds, steam headers or branch pipes.

This PhD project is a step change towards the fluid flow prediction within the polymer electrolyte fuel cells through micro/nano characterisation of porous layers of the fuel cell. X-ray micro/nano tomography has been developed to reveal a three dimensional digital image of gas diffusion layers at micro/nano scale and focused ion beam/scanning electron microscope nanotomography technique was developed to visualize the three dimensional porous structure of the microporous layer and catalyst layer. Tomography images then were used to obtain morphological parameters of the layers and combined with well-known analytical models and numerical-simulations to anticipate the permeability, diffusivity and tortuousity of the layers. The project can be divided into two main sections. In the first section X-ray micro and nanotomography were used to characterise the uncompressed gas diffusion layers. In addition, the structural features of compressed gas diffusion layers were captured by using polydimethylsiloxane to encapsulate the compressed porous structure and by subsequently employing X-ray microtomography to reconstruct a digital three dimensional model. In the second section, focused ion beam/scanning electron microscope nanotomography was developed for the microporous layer and the catalyst layer. The techniques were successfully applied to other materials including glass micropipettes, metals, silicon, urine catheters and diatomaceous frustules.

Following a comprehensive literature review on the machinability of nickel based superalloys using conventional carbide, coated carbide and ceramics including uncoated/coated PCBN, the research details statistically designed experimental work to assess the tool life/wear performance and workpiece surface integrity of a range of uncoated and coated PCBN tools, when turning solution treated and aged Inconel 718. Typically, the use of carbide tooling is limited to < 60 m/min cutting speed, even with the use of high pressure cutting fluids (JetStream systems). Hardmetal coatings provide some productivity improvements although cutting speed restrictions still operate. Details of PCBN use at up to 600 m/min have been published but at the expense of tool life. Experimental testing of a number of uncoated PCBN grades involving both high and low CBN concentrations, indicated a preferred operating window of ~ 300 – 400 m/min. Advanced ceramic coatings provided no significant benefits. Primary tool wear mechanisms related to abrasion, workpiece adhesion/diffusion and fracture depending on the specific operating parameters employed. In depth workpiece integrity evaluation involving surface roughness, microstructure, microhardness and residual stress measurement suggested only limited damage when operating with PCBN tooling at preferred/optimised conditions.

The work reported details the machinability of the gamma titanium aluminide intermetallic (-TiAl) Ti-45Al-8Nb-0.2C currently under evaluation to be the material of choice for blades and stators in the intermediate compressor (IP) and low pressure (LP) turbine sections of an aeroengine due to the alloys high temperature (~800C) and low weight properties. Following a literature review, the thesis details the results from two phases of experimental work. The first focused on high speed milling trials using coated tungsten carbide ball nose end mills with various operating parameters whilst the second phase provided an assessment of intermittent dress creep feed grinding using both conventional (SiC) and superabrasive (diamond and CBN) wheels with free jet nozzles. Benchmarking of the -TiAl alloy against other -TiAl (Ti-45Al-2Mn-2Nb +0.8%vol. TiB2), burn resistant and conventional titanium (Ti-6Al-4V) alloys was also performed. Full and fractional factorial (Taguchi) experimental designs were employed to identify the effect of key operating factors and levels on output measures (tool life/wheel wear, forces, power, and workpiece surface roughness). Taguchi main effect plots are detailed, together with Analysis of Variance (ANOVA) data and percentage contribution ratio (PCR) values. In addition, workpiece surface integrity evaluation including assessment of microstructure and microhardness is also presented.

An indirect conversion radioisotopic battery (ICRB) and capacitor power source was designed, simulated, manufactured and tested in this research. All ICRBs manufactured during this research used tritium (\(^3\)H) as the radioisotope in the form of gaseous tritium light sources (GTLSs). The operation of an ICRB was theoretically modelled from the generation of radiation particles right up to the storage of electrical energy in the capacitor. Comparison of simulation results with laboratory testing found close agreement particularly in the area of GTLS light emission, though the photovoltaic cell model was found to require further improvement. The ICRB was designed to provide power to a wireless sensor network (WSN) sensor node which would be buried underground and would report on the condition of a buried asset (e.g. water pipe). The most powerful ICRB generated 1.6\(\mu\)W, 60% more than the 1.0\(\mu\)W necessary to power a WSN sensor node. This ICRB would provide useful power to the WSN sensor node for 4.24 years. The greatest achieved efficiency of ICRB and capacitor system was 0.6% which compares favourably with ICRBs produced by other researchers. An ICRB was buried on a working water pipe for a duration exceeding two months and continues to function as predicted.

After decades of investigating brake noise using advanced tools and methods, brake squeal remains a major problem of the automotive industry. The Finite Element Analysis (FEA) method has long been used as a means of reliable simulation of brake noise, mainly using the Complex Eigenvalue Analysis (CEA) to predict the occurrence of instabilities resulting in brake noise. However it has been shown that CEA often over-predicts instabilities. A major improvement for CEA proposed in this study is tuning the model with an accurate level of damping. Different sources of damping are investigated and the system components are tuned using Rayleigh damping method. Also, an effective representative model for the brake insulator is proposed. The FEA model of the brake system tuned with the damping characteristics highlights the actual unstable frequencies by eliminating the over-predictions. This study also investigates effectiveness of a hybrid Implicit-Explicit FEA method which combines frequency domain and time domain solution schemes. The time/frequency domain co-simulation analysis presents time-domain analysis results more efficiently. Frictional forces are known as a major contributing factor in brake noise generation. A new brake pad design is proposed, addressing the frictional forces at the disc-pad contact interface. This concept is based on the hypothesis that variation of frictional coefficient over the radius of the brake pad is effective in reducing the susceptibility of brake squeal.

The work in this thesis is concerned with further development of an Intelligent Knowledge-Based System (IKBS) for forging die design. It follows on from initial work carried out at the School of Manufacturing and Mechanical Engineering. The main parts of the original design for the system are a sequence design program (SDP) for two and three dimensional parts, an interface program which can be connected to a finite-element program for metal forming simulation and a Control Module which supervises these two parts and co-ordinates their activities. Of these three modules, only the SDP and the Control Module existed when the current work was started. The purpose of the work reported here is to develop, improve and validate the original system. Among the five different families of components within the original IKBS, Stub Axles have been selected for the current research work. An interface program has been written which can generate a datafile for the available finite-element program (EPFEP3). This interface program inputs one preform stage as the geometry for mesh generation and the corresponding product stage in order to determine the boundary conditions. It also inputs the data within the SDP database for completing the other parts of the datafile. This program is efficient, rapid and user friendly and can easily be extended for the other families of components in the SDP. In the IKBS, when a new component is input to the system, each forming stage of the component should be compared with the same stage of the same family of all the components stored in the database. To do so, the significant processing and geometrical parameters and also their weighting effects should be input to the system. A new experimentally-based approach has been developed to obtain the weighting effects of the significant parameters. The weighting factors obtained are saved in the knowledge-base and have been shown to lead to the correct predictions when data for real forgings was used. The method for obtaining the weighting effects of the significant parameters can be extended to the other families of components within the IKBS. Programs have been written to perform computer-aided reasoning in the IKBS. In particular, recognising and extracting the values of the significant parameters of the operational sequence of a component, creating the IKBS database based on real data and performing the comparison procedure for a new component stage with those stored in the IKBS database.

Recent trends to downsize diesel engines have increased the stress on lubricants. Oils naturally degrade during operation, undergoing continual reactions, changing chemically and physically, detracting in performance from initial specifications. This thesis investigates the role of fuel in the ageing of diesel engine oils, specifically Ultra Low Sulphur Diesel (ULSD) and Rapeseed Methyl Ester (RME – a common European biodiesel). Oil ageing is assessed distinctly with fuel dilution, the entrainment of exhaust gases; and the effects of soot loading. Results show fuel dilution has the greatest influence on oil performance. Effects are seen with an instant ‘dilution’ of properties, with the resultant blend performing as an amalgam of the fluids. This can be both positive and negative, depending on the property being measured, with the entrainment of biodiesel generally beneficial. The entrainment of exhaust gases in the oil leads to increased unburnt hydrocarbons and fuel content, with similar dilution effects. Soot loaded oil performance is heavily dependent on the respective fuel content. RME contamination has a positive influence which far outweighs its negligible soot production, whereas ULSD detracts from oil performance, also producing more soot. During an equivalent timeframe, the influence of RME is less detrimental than ULSD on overall performance.

The dynamic performance of a turbocharged diesel engine during transient operation has been studied. For appropriate analysis of data obtained from engine transient operation, four alternative automated filtering methods were implemented on the cycle-by-cycle in-cylinder pressure. The techniques to process instantaneous emission data and align the transient data from different analyzers were developed. In the experimental study, the effects of engine speed and EGR have been investigated through load increase tests at a constant engine speed with different EGR calibrations. Based on the experimental results, a real-time diesel engine model was developed by Simulink. The model is capable of simulating the main engine parameters. It included the air path model, combustion model and dynamic emission behavior model. The model can run as a real-time simulator for engine control strategy development. . An advanced fast predictive control approach was proposed and validated in a HIL simulation platform. The model predictive control was developed for EGR and VGT control. The oxygen concentration oriented control was designed and implemented in the real-time model. Compared with PID control, MPC presents a good tracking performance of reference values with a shorter response time. The results in HIL proved the real-time capability of the control strategy.